linux-kernel - [PATCH 06/10] coresight: perf: traceid: Add perf notifiers for trace ID

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Message-Id: <20220308205000.27646-7-mike.leach@linaro.org>
Date:   Tue,  8 Mar 2022 20:49:56 +0000
From:   Mike Leach <mike.leach@...aro.org>
To:     suzuki.poulose@....com, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
        acme@...nel.org, linux-perf-users@...r.kernel.org,
        leo.yan@...aro.org, Mike Leach <mike.leach@...aro.org>
Subject: [PATCH 06/10] coresight: perf: traceid: Add perf notifiers for trace ID

Adds in notifier calls to the trace ID allocator that perf
events are starting and stopping.

This ensures that Trace IDs associated with CPUs remain the same
throughout the perf session, and are only release when all perf
sessions are complete.

Signed-off-by: Mike Leach <mike.leach@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index c039b6ae206f..008f9dac429d 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -22,6 +22,7 @@
 #include "coresight-etm-perf.h"
 #include "coresight-priv.h"
 #include "coresight-syscfg.h"
+#include "coresight-trace-id.h"
 
 static struct pmu etm_pmu;
 static bool etm_perf_up;
@@ -223,11 +224,21 @@ static void free_event_data(struct work_struct *work)
 		struct list_head **ppath;
 
 		ppath = etm_event_cpu_path_ptr(event_data, cpu);
-		if (!(IS_ERR_OR_NULL(*ppath)))
+		if (!(IS_ERR_OR_NULL(*ppath))) {
 			coresight_release_path(*ppath);
+			/*
+			 * perf may have read a trace id for a cpu, but never actually
+			 * executed code on that cpu - which means the trace id would
+			 * not release on disable. Re-release here to be sure.
+			 */
+			coresight_trace_id_put_cpu_id(cpu, coresight_get_trace_id_map());
+		}
 		*ppath = NULL;
 	}
 
+	/* mark perf event as done for trace id allocator */
+	coresight_trace_id_perf_stop();
+
 	free_percpu(event_data->path);
 	kfree(event_data);
 }
@@ -314,6 +325,9 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		sink = user_sink = coresight_get_sink_by_id(id);
 	}
 
+	/* tell the trace ID allocator that a perf event is starting up */
+	coresight_trace_id_perf_start();
+
 	/* check if user wants a coresight configuration selected */
 	cfg_hash = (u32)((event->attr.config2 & GENMASK_ULL(63, 32)) >> 32);
 	if (cfg_hash) {
-- 
2.17.1